This variant uses the hardware available from the Makerbot store - just tweaks the hinge point to ensure it fits and works under the Replicator dual top mount.

Instructions

The source files are there if you want to tweak things further for any reason. The original suggestion of setting the wall thickness to 3 and fill to 10% works well.

UPDATE: There is an additional STL which has been exported from Rhino3D with some different settings which should make it easier to print with the latest version of Makerware. (The previous version works fine with Skeinforge/ReplicatOrg)